Temperature Controlled Loadlock Chamber

ABSTRACT

A temperature controlled loadlock chamber for use in semiconductor processing is provided. The temperature controlled loadlock chamber may include one or more of an adjustable fluid pump, mass flow controller, one or more temperature sensors, and a controller. The adjustable fluid pump provides fluid having a predetermined temperature to a temperature-controlled plate. The mass flow controller provides gas flow into the chamber that may also aid in maintaining a desired temperature. Additionally, one or more temperature sensors may be combined with the adjustable fluid pump and/or the mass flow controller to provide feedback and to provide a greater control over the temperature. A controller may be added to control the adjustable fluid pump and the mass flow controller based upon temperature readings from the one or more temperature sensors.

TECHNICAL FIELD

This invention relates generally to the fabrication of semiconductordevices and, more particularly, to a method and structure to control thetemperature of a wafer in a loadlock.

BACKGROUND

As integrated circuit feature sizes decrease, the gate dielectricthickness of field effect transistors (FETs) also decreases. Thisdecrease is driven in part by the demands of overall device scaling. Asgate conductor widths decrease, for example, other device dimensionsdecrease to maintain the proper device scale, and thus device operation.Another factor driving gate dielectric thickness reduction is theincreased transistor drain current realized from a reduced gatedielectric thickness. The transistor drain current is proportional tothe amount of charge induced in the transistor channel region by thevoltage applied to the gate conductor. The amount of charge induced by agiven voltage drop across the dielectric is a factor of the capacitanceof the gate dielectric.

In order to achieve increased capacitance, gate dielectrics made fromoxides such as SiO_(x) are now as thin as 10 Å. These extremely thingate oxides result in increased gate-to-channel leakage current,however. Problems such as this have led to the use of materials thathave dielectric constants that are greater than the dielectric constantof silicon oxide, which has a k value of about 3.9. Higher k values, forexample 20 or more, may be obtained with various transition metaloxides, such as an oxynitride film. These high-k materials allow highcapacitances to be achieved with relatively thick dielectric layers. Inthis manner, the reliability problems associated with very thindielectric layers can be avoided while improving transistor performance.

There are, however, fabrication problems associated with forming gatedielectric layers that include high-k materials. Generally,semiconductor fabrication utilizes one or more cluster tools, whichcomprises various process chambers that can be utilized in associationwith a wafer handling system or device to perform a variety ofsemiconductor processes. These processes can include, for example,oxidation, nitridation, annealing, deposition processes, and the like.

In the example of forming a gate dielectric comprising an oxynitridefilm, a cluster tool may be used to perform an oxidation process, anitridation process, and an anneal process, wherein each process istypically performed in different process chambers. Between chambers, awafer is transferred through a loadlock chamber. The loadlock chambertypically has a non-adjustable cooling plate maintained at a specifictemperature to cool the wafer. The oxidation chamber, however, fails tomaintain a uniform temperature across the wafer. It has been found thatthis variation in the temperature across the wafer may result in avariation in the equivalent oxide thickness (EOT), which in turn resultsin a variation of the Idsat between FETs. This variation may be observednot only with FETs on different wafers, but also between FETs ondifferent dies on a single wafer and between FETs on a single die. Thevariation in the Idsat may adversely affect the circuitry and reduceyield, thereby increasing costs.

Accordingly, there is a need for a method and a structure to maintain amore uniform temperature over a wafer during processing.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, andtechnical advantages are generally achieved by preferred embodiments ofthe present invention that provide a method and structure to maintain amore uniform temperature across a wafer during processing.

An embodiment of the invention provides a loadlock chamber forsemiconductor processing. The loadlock includes a chamber, atemperature-controlled plate within the chamber and a chiller. Thetemperature-controlled plate has a first intake port and a first outputport interconnected by tubing. The chiller has a second output portcoupled to the first intake port and a second intake port coupled to thefirst output port. The chiller has an adjustable temperature for whichthe chiller may provide cooling fluid to the temperature-controlledplate via the second output port and the first intake port.

In another embodiment of the present invention, another loadlock chamberfor semiconductor processing is provided. The loadlock chamber includesa chamber, a temperature-controlled plate within the chamber, anadjustable chiller, and a mass flow controller. The adjustable chilleris coupled to the temperature-controlled plate. The mass flow controlleris coupled to a gas intake port in the chamber and allows a flow of gasinto the chamber.

In another embodiment of the present invention, another loadlock chamberfor semiconductor processing is provided. The loadlock chamber includesa chamber, a mass flow controller, a cooling plate, an adjustablechiller, one or more temperature sensors, and a controller. The coolingplate is located in an interior region of the chamber and is coupled tothe chiller to allow the chiller to flow fluid at an adjustabletemperature through the cooling plate. The controller is communicativelycoupled to the one or more temperature sensors, the adjustable chiller,and the mass flow controller. The controller receives temperaturereadings from the one or more temperature sensors and adjusts one orboth of the flow of gas through the mass flow controller and atemperature of the fluid flowing through the adjustable chiller.

Additional features and advantages of embodiments of the invention willbe described hereinafter, which form the subject of the claims of theinvention. It should be appreciated by those skilled in the art that thespecific embodiments disclosed might be readily utilized as a basis formodifying or designing other structures or processes for carrying outthe purposes of the present invention. It should also be realized bythose skilled in the art that such equivalent constructions andvariations on the example embodiments described do not depart from thespirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic of a loadlock chamber in accordance with anembodiment of the present invention;

FIG. 2 is a block diagram of a loadlock chamber in accordance with anembodiment of the present invention; and

FIG. 3 is a flow chart illustrating a process of controlling thetemperature of a wafer in a loadlock chamber in accordance with anembodiment of the present invention.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the preferredembodiments and are not necessarily drawn to scale. To more clearlyillustrate certain embodiments, a letter indicating variations of thesame structure, material, or process step may follow a figure number.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The operation and fabrication of the presently preferred embodiments arediscussed in detail below. However, the embodiments and examplesdescribed herein are not the only applications or uses contemplated forthe invention. The specific embodiments discussed are merelyillustrative of specific ways to make and use the invention, and do notlimit the scope of the invention or the appended claims.

Exemplary structures and methods are provided below for fabricating ametal oxide semiconductor field effect transistor (MOSFET) according toembodiments of the invention. Although the exemplary embodiments aredescribed as a series of steps, it will be appreciated that this is forillustration and not for the purpose of limitation. For example, somesteps may occur in a different order than illustrated yet remain withinthe scope of the invention. In addition, not all illustrated steps maybe required to implement the present invention. Furthermore, thestructures and methods according to embodiments of the invention may beimplemented in association with the fabrication or processing of othersemiconductor structures not illustrated.

FIG. 1 schematically illustrates a cluster tool 100 in accordance withan embodiment of the present invention. The cluster tool 100 includes afirst process chamber 112, a second process chamber 114, and a thirdprocess chamber 116 interconnected via a buffer chamber 120. In anembodiment, the first process chamber 112 is configured as an oxidationchamber, the second process chamber 114 is configured as a nitridationchamber, and the third process chamber 116 is configured as an annealingchamber, such as an RTA chamber, which preferably has an oxidizingambient such as oxygen. Interconnected to the buffer chamber 120 are oneor more loadlock chambers 121. The buffer chamber 120 and the one ormore loadlock chambers 121 permit transferring one or more wafersbetween the first process chamber 112, the second process chamber 114,and the third process chamber 116 without breaking vacuum betweenprocesses or chambers.

The cluster tool 100 may optionally further include a front-openingunified pod (FOUP) docking system 122 and a factory interface 124. TheFOUP docking system 122 and the factory interface 124 allow wafers to beloaded and unloaded without exposing the loadlock chambers 121, thebuffer chamber 120, the first process chamber 112, the second processchamber 114, and the third process chamber 116 to air. The pressure ofthe FOUP docking system 122 is usually at about 1 atm (same as the fabenvironment), whereas that of a loadlock chamber 121 is much lower,typically under vacuum, e.g., less than about 10 Torr.

In operation, wafers are transferred into and out of the cluster tool100, either individually or in batches, via the FOUP docking system 122.The wafers are transferred from the FOUP docking system 122 to theloadlock chamber 121 via the factory interface 124. Once transferredinto the loadlock chambers 121, the wafers are isolated from the ambientenvironment. Typically, an inert gas such as nitrogen is purged throughthe loadlock chamber 121, which is pumped down to a low pressure, if notvacuum, typically ranging from 200 to 1000 Pa, to remove any air fromthe atmosphere. The wafers are transferred to one or more of the firstprocess chamber 112, the second process chamber 114, and the thirdprocess chamber 116, which are also pumped down to a similar pressure tobe in equilibrium with the pressure of the loadlock chambers 121, viathe buffer chamber 120.

Processing may begin by one or more wafers being transferred from one ormore of the loadlock chambers 121 into a processing chamber, e.g., thefirst process chamber 112, the second process chamber 114, and the thirdprocess chamber 116, using a belt, robotic arm, or other well-knowntransfer mechanism (not shown). Each of the processing chambers may beequipped with heating elements, gas flow orifices, radio frequencycoils, and other equipment (not shown) necessary to affect the desiredprocess.

In the illustrative embodiment, an oxide layer is deposited in the firstprocess chamber 112. After formation of an oxide layer, the wafer istransferred from the first process chamber 112, via loadlock chambers121, to the second process chamber 114. Thermal or plasma nitridation isperformed in the second process chamber 114. Note that by utilizingcluster tool 100, vacuum need not be broken when transferring the waferbetween processing chambers. This eliminates the possibility of thereactions of wafers with air or the moisture in the air. This alsoreduces the possibility of damage to the wafer from handling and thelikelihood of contamination arising from exposure to the ambientenvironment. After nitridation, the wafer is transferred from the secondprocess chamber 114, via the loadlock chambers 121, again withoutbreaking vacuum, to the third process chamber 116 where the wafer isannealed.

It should be noted that FIG. 1 illustrates cluster tool 100 having threeprocess chambers for illustrative purposes only. Other embodiments mayinclude fewer or more process chambers. Additionally, other embodimentsmay utilize some, all, or none of the process chambers given above asexamples. Embodiments of the present invention may be utilized, forexample, in any cluster tool or other processing equipment wherein it isdesirable to control the temperature of a wafer as it is beingtransported from a first location to a second location.

FIG. 2 illustrates a cross section view of a loadlock chamber 200, whichmay be used as one or more of the loadlock chambers 121 of FIG. 1, inaccordance with an embodiment of the present invention. One of ordinaryskill in the art will realize that FIG. 2 schematically illustrates anembodiment of the present invention and an actual embodiment of theinvention may take any shape or form.

Generally, the loadlock chamber 200 comprises an enclosed chamber 210having a top 212, a bottom 214, and sidewalls 216. Holders 218 arepositioned to hold one or more wafers during transport. Atemperature-controlled plate 220 is positioned along the bottom 214 andis coupled to an adjustable chiller 222. The chiller 222 providescooling water to the temperature-controlled plate 220. In an embodiment,the chiller 222 is adjustable to supply a cooling liquid, such as water,having an adjustable temperature to the temperature-controlled plate220. The chiller 222 may also be adjusted to provide the cooling liquidat an adjustable pressure. Generally, the temperature-controlled plate220 includes tubing made of a material having good thermal conductivityproperties. In an embodiment, copper tubing is used and the chiller 222is adjustable to provide the cooling liquid having a temperature fromabout 17° C. to about 120° C., but more preferably from about 30° C. toabout 90° C. Additionally, it is preferred that the chiller 222 and thetemperature-controlled plate 220 are a pressurized system having apressure ranging from about 1 atm to about 10 atm.

The temperature-controlled plate 220 may also include raised portions,such as a plurality of pins 223 upon which a wafer may rest. The heightof the plurality of pins 223 may be adjusted to maximize the coolingeffect, including the rate of cooling, needed for a particularapplication. For example, it has been found that the height of the pinsmay be reduced to shorten the period of time required to cool the waferto a specific temperature. In an embodiment, the height of the pluralityof pins 223 is between about 1 mm and about 0.1 mm. Other heights,however, may be used. It should also be noted that other shapes may beused. For example, the pins may be any shape and may comprise ridges ora spiral shape on the temperature-controlled plate 220.

FIG. 2 also illustrates a mass flow controller 230 and a control valve232 in accordance with an embodiment of the present invention. The massflow controller 230 and the control valve 232 act together to create andmaintain a gas atmosphere within the loadlock chamber 200. Inparticular, the mass flow controller 230 is coupled to a source gas 234to control the flow of gas into the loadlock chamber 200, and thecontrol valve 232 is coupled to the loadlock chamber 200 to release gasfrom within the loadlock chamber 200 by pump. In an embodiment, the massflow controller 230 and the control valve 232 cooperate to maintain aspecific pressure within the loadlock chamber 200. Preferably, the massflow controller 230 and the control valve 232 are configured to maintainan atmospheric pressure within the loadlock chamber 200 from about 3Torr to about 760 Torr.

In a preferred embodiment, the loadlock chamber 200 includes atemperature sensor 240, such as an infra-red temperature sensor,communicatively coupled to a controller 242, which may also becommunicatively coupled to the chiller 222, the mass flow controller230, and/or the control valve 232. In this embodiment, the controller242 receives temperature information from the temperature sensor 240 andautomatically controls the chiller 222, the mass flow controller 230,and/or the control valve 232 to maintain a desired temperature. Thedesired temperature may be based upon, among other things, the previousprocess, the subsequent process, the wafer size and thickness, and thelike.

It should also be noted that FIG. 2 illustrates a single temperaturesensor 240 for illustrative purposes only. It may be desirable in someembodiments of the present invention to utilize multiple temperaturesensors, and possibly different types of temperature sensors. Forexample, multiple temperature sensors may be positioned in variouslocations within the loadlock chamber 200 to provide temperaturemeasurements in various regions of the wafer. The locations may include,for example, various locations across the wafer as well as both sides ofthe wafer.

FIG. 3 is a flow diagram illustrating a procedure that may be performedto control the temperature of a wafer in accordance with an embodimentof the present invention. The process begins in step 305, wherein adesired temperature is set. The desired temperature may be set by auser, read from a database, or the like. It should be noted that thedesired temperature may be based upon the process or processes beingperformed on the wafer. For example, the desired temperature may be setto a first temperature immediately after a first process has beenperformed to cause the temperature of the wafer to decrease slowly orquickly, or to cause the temperature of the wafer to increase slowly orquickly. A second process may require different temperatures. As anotherexample, it may be desirable to maintain a specific wafer temperatureprior to performing a specific process.

The process then proceeds to step 310, wherein one or more temperaturesamples are received. The temperature samples may be received from asingle temperature sensor or from multiple temperature sensors placed indifferent locations within the loadlock chamber 200. For example,temperature sensors may be placed across the top surface 212 of theloadlock chamber 200 spaced apart such that the temperature sensorsmeasure different portions of the wafer, including around the perimeterand the interior of the wafer. Additional temperature sensors may beplaced to measure the temperature along the bottom of the wafer.

In step 312, a determination is made whether or not the temperatureneeds adjusting. The desired temperature (see step 305) is compared tothe temperature samples and an adjustment, if necessary, is determined.If a determination is made that an adjustment is necessary, thenprocessing proceeds to step 314, wherein an adjustment is made. Theadjustment may include, for example, increasing the gas flow andpressure via the mass flow controller 230, reducing the gas flow andpressure via the mass flow controller 230 and the control valve 232,adjusting the temperature of the cooling fluid supplied by the chiller222, adjusting the flow rate of the cooling fluid supplied by thechiller 222, and/or the like.

If in step 312 a determination is made that an adjustment is notnecessary, then processing returns to step 310, wherein new temperaturesamples are received for processing.

It should be noted that the embodiment of the present inventiondiscussed above assumes that the loadlock chamber 200 be equipped withboth an adjustable chiller and a mass flow controller for providingtemperature adjustment by fluid and gas, respectively. Embodiments ofthe present invention, however, may utilize one or more of thesefeatures. For example, an embodiment of the present invention mayutilize an adjustable chiller, another embodiment of the presentinvention may utilize an adjustable chiller with a temperature sensor,another embodiment of the present invention may utilize a mass flowcontroller to maintain a specific temperature, another embodiment of thepresent invention may utilize a mass flow controller with a temperaturesensor, and another embodiment may utilize an adjustable chiller, a massflow controller, and a temperature sensor.

One of ordinary skill in the art will realize that the temperaturecontrolled loadlock chamber disclosed herein provides dynamic controlsand a feedback loop for maintaining optimum temperatures for a specificprocess. In this manner, more uniform semiconductor devices, includingmore uniform gate dielectrics, may be created. The increased uniformitywill enable more accurate and uniform circuits to be created.

Although embodiments of the present invention and their advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.For example, it will be readily understood by those skilled in the artthat many of the features, functions, processes, and materials describedherein may be varied while remaining within the scope of the presentinvention. Moreover, the scope of the present application is notintended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present invention,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed, thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present invention. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1. A loadlock chamber for semiconductor processing, the loadlock chambercomprising: a chamber having sidewalls, a top, and a bottom; atemperature-controlled plate within the chamber, thetemperature-controlled plate having a first intake port and a firstoutput port; and a chiller having a second output port coupled to thefirst intake port and a second intake port coupled to the first outputport, the chiller having an adjustable temperature within a range oftemperatures at which the chiller may provide cooling fluid to thetemperature-controlled plate via the second output port and the firstintake port.
 2. The loadlock chamber of claim 1, further comprising amass flow controller providing gas to an interior region of the chamber.3. The loadlock chamber of claim 2, further comprising: one or moretemperature sensors within the chamber; and a controller communicativelycoupled to the one or more temperature sensors and to the mass flowcontroller, the controller adjusting a flow rate of the gas supplied bythe mass flow controller based at least in part on one or moretemperature samples received from the one or more temperature sensors.4. The loadlock chamber of claim 1, wherein the temperature-controlledplate includes a plurality of pins.
 5. The loadlock chamber of claim 1,further comprising: one or more temperature sensors within the chamber;and a controller communicatively coupled to the one or more temperaturesensors and to the chiller, the controller adjusting the adjustabletemperature based at least in part on one or more temperature samplesreceived from the one or more temperature sensors.
 6. The loadlockchamber of claim 1, wherein the chiller provides cooling liquid at apressure of about 1 atm to about 10 atm.
 7. The loadlock chamber ofclaim 1, wherein the range of temperatures is about 17° C. to about 120°C.
 8. A loadlock chamber for semiconductor processing, the loadlockchamber comprising: a chamber having sidewalls, a top, and a bottom; atemperature-controlled plate within the chamber; an adjustable chillercoupled to the temperature-controlled plate, the adjustable chillerproviding cooling liquid to the temperature-controlled plate; a gasintake port in the chamber; and a mass flow controller coupled to thegas intake port, the mass flow controller allowing a flow of gas intothe chamber.
 9. The loadlock chamber of claim 8, wherein the gascomprises nitrogen or helium.
 10. The loadlock chamber of claim 8,wherein the adjustable chiller provides cooling liquid at a pressure ofabout 1 atm to about 10 atm.
 11. The loadlock chamber of claim 8,wherein the adjustable chiller is configured to provide cooling liquidat any temperature between about 17° C. and about 120° C.
 12. Theloadlock chamber of claim 8, further comprising one or more temperaturesensors mounted within the chamber.
 13. The loadlock chamber of claim12, further comprising a controller communicatively coupled to the oneor more temperature sensors, the controller controlling at least one ofa temperature or a pressure of the cooling liquid provided by theadjustable chiller to the temperature-controlled plate based at least inpart on the one or more temperature sensors.
 14. The loadlock chamber ofclaim 12, further comprising a controller communicatively coupled to theone or more temperature sensors, the controller controlling the flowrate of gas into the chamber by the mass flow controller based at leastin part on the one or more temperature sensors.
 15. A loadlock chamberfor semiconductor processing, the loadlock chamber comprising: a chamberhaving an interior region and an exterior region, the chamber having afirst port; a mass flow controller coupled to the chamber, the mass flowcontroller providing gas to the interior region of the chamber; acooling plate in the interior region of the chamber; an adjustablechiller coupled to the cooling plate, the adjustable chiller flowingfluid at an adjustable temperature through the cooling plate; one ormore temperature sensors in the interior region of the chamber; and acontroller communicatively coupled to the one or more temperaturesensors, the adjustable chiller, and the mass flow controller, thecontroller configured to receive one or more temperature samples fromthe one or more temperature sensors and to adjust the mass flowcontroller or the adjustable chiller based upon the one or moretemperature samples.
 16. The loadlock chamber of claim 15, wherein thegas comprises nitrogen or helium.
 17. The loadlock chamber of claim 15,wherein the adjustable chiller provides cooling liquid at a pressure ofabout 1 atm to about 10 atm.
 18. The loadlock chamber of claim 15,wherein the adjustable chiller is configured to provide cooling liquidat any temperature between about 17° C. and about 120° C.
 19. Theloadlock chamber of claim 15, wherein the controller adjusts thetemperature of the fluid at which the adjustable chiller providescooling liquid to the cooling plate.
 20. The loadlock chamber of claim15, wherein the controller adjusts the flow rate of gas supplied by themass flow controller.